Establishing ion transport channels in plastic crystal electrolytes via multifunctional cross-linked polymer matrices for stable and safe lithium metal batteries

Abstract

Despite the excellent ionic conductivity and thermal stability of succinonitrile (SN)-based plastic crystalline electrolytes (SPCEs), their reduction stability is suboptimal, causing undesirable interfacial side reactions. Incorporating a polymer matrix addresses these issues but limits polymer chain mobility, thereby reducing the actual ionic conductivity below expectations. To overcome these challenges, we propose a multifunctional in situ crosslinked polymer matrix (polymeric tris(2-acryloyloxyethyl) isocyanurate, PIATE) to modulating ion transport properties of SPCE. This modification enhances mutual solubility, suppresses SN crystallization, and establishes a rapid ion transport pathway (polymer···[SN···Li⁺]), significantly boosting ionic conductivity. PIATE-modified SPCE also features finely tuned energy levels and concentrated coordination structures, broadening the electrochemical window and forming stable Li₃N-rich solid electrolyte interphases. Moreover, the isocyanuric acid groups in PIATE release non-flammable gases like nitrogen and water vapor upon thermal decomposition, enhancing fire safety. Consequently, the modified SPCE exhibits improved room temperature ionic conductivity (1.6 mS cm⁻¹), high lithium-ion transference number (0.72), and extended electrochemical window (5.2 V). Electrochemical tests show enhanced stability in Li symmetric, Li||LiFePO₄, and Li||LiCoO₂ cells (up to 4.6 V). The high thermal stability and safety have been further demonstrated in the Li||NCM811 pouch cells, highlighting its potential for practical applications in lithium metal batteries.